1. Field of the Invention
The present invention relates to an ink jet recording apparatus, particularly to an ink jet recording apparatus using a photo curing ink.
2. Description of Related Art
A lot of ink jet recording apparatuses are used at present because each of them only generates comparatively small noises under printing and has a high print quality.
An ink jet recording apparatus forms an image on a recording medium such as paper by moving relative positions of a recording head and the recording medium while using a piezoelectric device, heater device or the like, jetting ink from a nozzle of the recording head as minute droplets toward the recording medium, and infiltrating or fixing the ink into or in the recording medium.
An ink jet recording apparatus includes for example, the serial head type for forming an image by reciprocating a recording head on a recording medium and feeding the recording medium in a direction orthogonal to the scanning direction of the recording head, and the line head type for forming an image by using a recording head fixed with a nozzle string covering the recording width of the recording medium and feeding the recording medium in a direction vertical to the direction of the recording width of the recording medium.
At present, in the field of such as printing for commercial products and commercial-product packaging materials, needs for small-lot production are increased and the frequency of using an ink jet system capable of producing a mall lot at a low cost is increased compared to a system requiring plate making such as a gravure printing system or flexographic printing system.
As well known, materials having no absorbability such as resin and metal are frequently used for commercial products and commercial-product packaging materials.
To use one of these materials having no absorbability as a recording medium, a photo curing type of ink jet recording apparatus is developed which cures and fixes a high viscosity, photo curing ink by jetting the ink onto a recording medium and attaching the ink to the recording medium and then irradiating the medium with light such as ultraviolet rays in order to make it possible to fix the ink to the recording medium.
In the earlier development, such photo curing type of ink jet recording apparatus includes an ultraviolet curing type of ink jet recording apparatus which is hitherto practically used and which is constituted so as to irradiate much ultraviolet rays in the block by using a radical polymerization ink. Moreover, it is proposed to use a light source for irradiating the light having a directivity such as a laser beam (for example, refers to JP-Tokukai 2001-310454). Specifically, a semiconductor laser and a light emitting diode are known as light sources for irradiating the light having a directivity.
The use of a semiconductor laser or light emitting diode reduces the calorific value for irradiation and power consumption. Moreover, a light source unit is downsized compared to the case of a fluorescent lamp or a high pressure mercury lamp. Further, the semiconductor laser and light emitting diode are stable and easy in adjustment of light intensity.
However, the above earlier development has the following problem.
When a radical polymerization ink is used, it is necessary to irradiate a comparatively large amount of ultraviolet rays. Therefore, it is a problem that a high-output light source apparatus must be mounted, leading to the increase of its size and fabrication cost.
To solve the above problems, it is considered to use a cationic polymerization ink which is not practically used at present. However, because the cationic polymerization ink has an unstable physical property such as temperature dependence and a physical property of causing a curing reaction due to weak light such as reflected light, it is difficult to handle the ink and thereby, this makes practical use of it difficult.
For example, when the illumination to ink is lowered due to deterioration resulted from the long-term use of a light source or as the light source is made closer to a recording head because of a request for downsizing a recording apparatus, the illumination is lowered due to ink mist. Under the above situation, when the cationic polymerization ink having the above physical property is used, a curing trouble easily occurs and thereby, the ink cannot be practically used.
It is considered to measure the influence of a light source due to the ink mist as a change of light intensities and reflect the measurement result on the lighting operation of the light source. Particularly in the case of light intensity measurement, normal measuring instruments respectively have a specific temperature characteristic and a slight fluctuation occurs in measurement results due to an ambient temperature. Thereby, such fluctuation becomes a measurement error. Therefore, there was a problem that it was difficult to accurately measure the influence of a light source due to ink mist.